1. Field of the Invention
The present invention relates to improvement in a method for producing an optical fiber ribbon in which a plurality of coated optical fibers are arranged in a plane and integrated in the form of a ribbon
2. Description of the Related Art
Conventionally, as a method for producing an optical fiber ribbon, Unexamined Japanese Patent Publication (kokai) No. Hei-1-250911 discloses a method in which coated optical fibers are passed through a narrowing roller while they are being displaced in a direction perpendicular to the direction of the arrangement of the coated optical fibers to thereby suppress the force urging the coated optical fibers to separate from one another at the time of the narrowing of the coated optical fibers.
In this case, because the coated optical fibers are passed through the narrowing roller while they are being displaced in a direction perpendicular to the direction of the arrangement of the coated optical fibers, the work of adjusting the position of the narrowing roller both in the direction of the arrangement of the coated optical fibers and in a direction perpendicular to the direction of the arrangement of the coated optical fibers becomes very delicate if the optical fibers are to be arranged in a plane without any gap in a coater. Accordingly, the narrowing roller is disadvantageous in that adjustment is troublesome and workability is poor.
Further, Unexamined Japanese Patent Publication (kokai) No. Sho-63-161418 discloses a method in which coated optical fibers are configured in linearly vertical line and arranged by a plurality of rollers each having a U-shaped surface as its outer circumferential surface.
In this case, when the rollers each having the U-shaped surface rotate at a high speed, vibration occurs in rotation shafts because the rotation shafts have slight vibration caused by idling of ball bearings, or the like. At that time, the respective coated optical fibers move on the outer circumferential surfaces of the rollers toward the roller end portions, so that the respective coated optical fibers become disordered. Accordingly, the arrangement of the optical fiber ribbon thus obtained becomes poor.
Accordingly, in the case where a plurality of rollers each having a U-shaped surface in its outer circumference are used in high-speed production, there is a disadvantage that the respective coated optical fibers particularly located at ends are displaced laterally on the U-shaped surfaces to thereby make the arrangement poor.
Further, Examined Japanese Utility Model Publication No. Hei-4-49603 discloses a method in which coated optical fibers are arranged by two kinds of grooved rollers which are set in the directions of the width and thickness of the optical fiber ribbon respectively.
In this case, the groove dimensions of the rollers must be specified with sufficient allowance for any variation that may exist depending on the different production lots with respect to not only the outside diameter of the respective coated optical fibers but also the overall dimensions of the fiber ribbons. It is, therefore, difficult to obatin an exact arrangement of the coated optical fibers by means of such groove rollers.
Further, when a plurality of coated optical fibers are forced to be put into a narrow groove, the coated optical fibers are pressed strongly against the groove so that the coated optical fibers are injured.